Treatment of water with uv/chlorine advanced oxidation

ABSTRACT

A process for decontaminating a contaminated aqueous liquid comprising methyl-tert-butyl ether (MTBE) involving pretreating the contaminated aqueous liquid with chlorine and/or a hypochlorous acid salt and irradiating the aqueous liquid with an ultraviolet wavelength to produce a radical molecular species that degrades the MTBE. MTBE is degraded into at least one degradation byproduct including tert-butyl formate (TBF), tert-butyl alcohol (TBA), acetone, carbon dioxide, and water.

BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to a water treatment process that includesoxidizing organic contaminants under exposure to ultraviolet light,especially as it relates to the removal of traces of methyltertiary-butyl ether (MTBE).

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

The chemical water pollutant, methyl tertiary butyl ether (MTBE), is awell-known groundwater contaminant which mainly originates frompetrochemical and transportation industries. Higher production levelsand widespread use of MTBE make it likely to be present in groundwatersources. Leakage from underground storage tanks and pipelines, spills,contaminated sites, releases from manufacturing, storage sites, and atgasoline filling stations account for the major sources of environmentalcontamination.

Contamination of drinking water with MTBE has raised considerableconcern among health officials and water suppliers. The US EnvironmentalProtection Agency considers MTBE to be a potential human carcinogen, andset an advisory level of 20-40 μg/L. See U.S. Environmental ProtectionAgency, (1997b). Drinking Water Advisory: Consumer Acceptability Adviceand Health Effects Analysis on Methyl Tertiary-Butyl Ether (MTBE).Washington, D.C.: U.S. Environmental Protection Agency, Office of Water,EPA-822-F-97-009. However, remediation of MTBE from water is challengingand expensive due to MTBE's high solubility in water (50,000 mg/l), lowbiodegradability, low Henry's constant, very low affinity for commonadsorbents, high mobility, and public health concern. See McCarthy &Tiemann, “MTBE in gasoline: clean air and drinking water issues”Congressional Research Service Reports, 2006; J. Reuter, Allen, &Goldman, “Methyl tert-butyl ether in surface drinking water supplies,”Health and environmental assessment of MTBE, UC Toxics Research andTeaching Program, UC Davis 3 (1998); J. E. Reuter et al., 1998,“Concentrations, Sources, and Fate of the Gasoline Oxygenate Methyltert-Butyl Ether (MTBE) in a Multiple-Use Lake,” Environmental Science &Technology, 32(23), 3666-3672, each incorporated herein by reference intheir entirety. Advanced oxidation processes (AOPs) have beenacknowledged as promising treatment technologies for water contaminatedwith MTBE. AOPs have shown great potential in removing organiccontaminants at low and high levels in groundwater, municipal andindustrial wastewater. See Kavanaugh, Michael, and Z. Chowdhury,“Removal of MTBE with advanced oxidation processes,” Iwa Publishing,2004, incorporated herein by reference in its entirety. Ultraviolet(UV)-driven AOPs are primarily based on the generation of powerfuloxidizing species, such as the hydroxyl radical (OH.). These processesmake use of hydroxyl radicals (OH.) to oxidize all organic pollutantspresent in water into carbon dioxide and water.

The chlorine based photochemical oxidation or UV/Cl2 is one type of AOPused to degrade organic contaminants. The photo-chemistry of theUV/chlorine process predominantly generates hydroxyl (OH) radical inaddition to chlorine radical. The pseudo-first-order rate constant forthe photolysis of HOCl and OCl⁻ at 330 nm (sunlight exposure) wasreported as 2×10⁻⁴ s⁻¹ and 1.2×10⁻³ s⁻¹, respectively. Sodiumhypochlorite (NaOCl) has been also used to oxidize secondary (2°)alcohols to ketones.

At favorable pH, free chlorine is available in water as an aqueoussolution. The photochemistry of UV/Cl₂ AOP is described by the reactionsbelow. See Jin, Jing, Mohamed Gamal El-Din, and James R. Bolton.“Assessment of the UV/Chlorine process as an advanced oxidationprocess.” water research 45.4 (2011): 1890-1896; Wang, Ding, James R.Bolton, and Ron Hofmann. “Medium pressure UV combined with chlorineadvanced oxidation for trichloroethylene destruction in a model water.”water research 46.15 (2012): 4677-4686, each incorporated herein byreference in their entirety.

Cl₂+H₂O→OCl+HCl  (1)

OCl→H⁺+OCl⁻(equilibrium with pKa=7.6 at 20° C.  (2)

OCl+UV photons→.OH+Cl.  (3)

OCl⁻+UV photons→.O⁻+Cl.  (4)

.O⁻+H₂O→.OH+OH⁻  (5)

The availability of free chlorine is dependent on the pH of thesolution, as discussed by several studies. In conventional processes thepercent availability of free chlorine species at room temperature may be99.7% HOCl, 52.3% HOCl+47.7% OCl⁻, and 99.6% OCl⁻ at pH 5, 7.5 and 10,respectively. See Chan, Po Yee, Mohamed Gamal El-Din, and James R.Bolton. “A solar-driven UV/Chlorine advanced oxidation process.” waterresearch 46.17 (2012): 5672-5682; Feng, Yangang, Daniel W. Smith, andJames R. Bolton. “Photolysis of aqueous free chlorine species (HOCl andOCl) with 254 nm ultraviolet light.” Journal of EnvironmentalEngineering and Science 6.3 (2007): 277-284; Mofidi, A. A., Min, J. H.,Palencia, L. S., & Coffey, B. M. (2002). Task 2.1: Advanced OxidationProcesses and UV Photolysis for Treatment of Drinking Water Submittedby: Sun Liang, James F. Green Metropolitan Water District of SouthernCalifornia La Verne, Calif. Submitted to: California Energy Commission,(January); Nowell, Lisa H., and Jürg Hoigné. “Photolysis of aqueouschlorine at sunlight and ultraviolet wavelengths-I. Degradation rates.”Water Research 26.5 (1992): 593-598.; Watts, Michael J., and Karl G.Linden. “Chlorine photolysis and subsequent OH radical production duringUV treatment of chlorinated water.” Water Research 41.13 (2007):2871-2878.; Weng, ShihChi, Jing Li, and Ernest R. Blatchley. “Effects ofUV 254 irradiation on residual chlorine and DBPs in chlorination ofmodel organic-N precursors in swimming pools.” water research 46.8(2012): 2674-2682.; Rick Bond, P. E., B. & V. Advanced OxidationProcesses: White's Handbook of Chlorination and AlternativeDisinfectants, Fifth Edition, (2010) 976-1002.; White, G. C., &International, B. and V. (2010). Chlorination and AlternativeDisinfectants (5th Edition). Wiley, each incorporated herein byreference in their entirety.

Only a few studies investigated the use of aqueous chlorine as thechemical oxidant for UV-driven AOP as an alternative to other chemicaloxidants like hydrogen peroxide, and ozone. Similar to UV/H₂O₂, AOPs,UV-induced chlorine AOPs (UV/Cl₂ AOP) produce hydroxyl and otherradicals when water dosed with aqueous chlorine in the form ofhypochlorous acid (HOCl) or hypochlorite ions (ClO⁻) and exposed to UVlight. Hypochlorous acid (HOCl) has higher UV absorbance and a lowerscavenging rate than H₂O₂. In contrast, ClO— scavenges OH radicals aboutfour orders of magnitude faster than HOCl or H₂O₂, indicating thatUV/Cl₂ AOPs are generally more efficient at lower water pH. UV/Cl₂ wasefficiently able to degrade trichloroethylene, Methylisoborneol in waterthan UV/H₂O₂ process. See Rosenfeldt, Erik, et al. “Tech Talk—Comparisonof UV-mediated Advanced Oxidation (PDF).” Journal-American Water WorksAssociation 105.7 (2013): 29-33.; Wang, Ding, James R. Bolton, and RonHofmann. “Medium pressure UV combined with chlorine advanced oxidationfor trichloroethylene destruction in a model water.” Water Research46.15 (2012): 4677-4686., each incorporated herein by reference in theirentirety. A solar-driven UV/chlorine AOP was able to degrade methyleneblue (MB) and cyclohexanoic acid (CHA) in water. Another study reportedthat UV/Chlorine AOP was also able to degrade emerging watercontaminants with considerable energy reduction. A few studiesinvestigated the use of UV/chlorine AOP for the degradation of organiccontaminants in water and wastewater. The quantum yield of OH radicalproduction from HOCl at a wavelength of 254 nm was found to be 1.4mol·s⁻¹ greater than that of hydrogen peroxide (1.0 mol·s⁻¹) whereasother studies found the quantum yields of HOCl and OCl⁻ are 1.0±0.1 and0.9±0.1, respectively. Still, others have reported molar absorptioncoefficient of 155 and 121 ε254/M-1 cm-1 for HOCl and OCl⁻,respectively. See Sichel, C., C. Garcia, and K. Andre. “Feasibilitystudies: UV/chlorine advanced oxidation treatment for the removal ofemerging contaminants.” Water Research 45.19 (2011): 6371-6380; Watts,Michael J., and Karl G. Linden, “Chlorine photolysis and subsequent OHradical production during UV treatment of chlorinated water.” WaterResearch 41.13 (2007): 2871-28781; Nowell, Lisa H., and Juirg Hoigné.“Photolysis of aqueous chlorine at sunlight and ultravioletwavelengths-II. Hydroxyl radical production.” Water Research 26.5(1992): 599-605. each incorporated herein by reference in theirentirety.

In view of the forgoing, one objective of the present disclosure is toprovide a process for the removal of MTBE and associated organiccompounds from aqueous solution using a UV/chlorine process, optionally,under a continuous flow regime for MTBE and associated organic compoundremoval from aqueous solutions by UV/chlorine process.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, a process for decontaminating acontaminated aqueous liquid comprising methyl-tert-butyl ether (MTBE),including mixing chlorine (Cl₂) and/or a hypochlorous acid salt with thecontaminated aqueous liquid to form a chlorinated aqueous liquid,comprising 10-50 ppm of chlorine and/or the hypochlorous acid salt,relative to the total mass of the chlorinated aqueous liquid, andirradiating the chlorinated aqueous liquid with light having awavelength of about 254 from a monochromatic light source that generatesa 254 nm wavelength of light or with a polychromatic light source havingwavelengths between 200 nm and 370 nm to produce a radical molecularspecies that degrades the MTBE into at least one degradation byproductselected from the group consisting of tert-butyl formate (TBF),tert-butyl alcohol (TBA), acetone, carbon dioxide and water and forms adecontaminated aqueous liquid, in which a concentration of MTBE in thecontaminated aqueous liquid is higher than a concentration of MTBE inthe decontaminated aqueous liquid.

In some implementations, the process includes mixing the chlorinatedaqueous liquid after irradiating with an oxygen radical generatingcompound.

In some implementations, the oxygen radical generating compound is O₃and/or H₂O₂.

In some implementations, the O₃ and/or H₂O₂ is added at 10-25 times theconcentration of the chlorine and/or the hypochlorous acid salt in thechlorinated aqueous liquid.

In some implementations, the concentration of the chlorine and/or sodiumhypochlorite is 10-50 times the concentration of the MTBE in thechlorinated aqueous liquid.

In some implementations, the process includes adjusting the pH of thecontaminated aqueous liquid to a pH of 5-7 before mixing.

In some implementations, the process includes adjusting the pH withhydrochloric acid, sulfuric acid, or sodium hydroxide.

In some implementations, the light source power is between 10-200 W.

In some implementations, the light source has an intensity between5×10⁻³ W/cm²-7×10⁻² W/cm².

In some implementations, the irradiating takes place for 20-45 minutes.

In some implementations, the radical molecular species is at least oneof a chlorine radical and a hydroxyl radical.

In some implementations, the concentration of MTBE is at least 1 ppm inthe contaminated aqueous liquid and the concentration of MTBE is reducedby more than 92% in the decontaminated aqueous liquid.

According to another aspect, a continuous flow process fordecontaminating a contaminated aqueous liquid comprisingmethyl-tert-butyl ether (MTBE), including flowing a contaminated aqueousliquid comprising water and the MTBE and pretreating the contaminatedaqueous liquid with chlorine and/or a hypochlorous acid salt to forminga to form a chlorinated aqueous liquid comprising 10-50 ppm of chlorineand/or the hypochlorous acid salt, relative to the total mass of thechlorinated aqueous liquid and irradiating the chlorinated aqueousliquid with light having a wavelength of about 254 nm from amonochromatic light source that generates a 254 nm wavelength of lightor with a polychromatic light source having wavelengths between 200 nmand 370 nm to produce a radical molecular species that degrades the MTBEinto at least one degradation byproduct selected from the groupconsisting of tert-butyl formate (TBF), tert-butyl alcohol (TBA),acetone, carbon dioxide and water and forms a decontaminated aqueousliquid, in which a concentration of MTBE in the contaminated aqueousliquid is higher than a concentration of MTBE in the decontaminatedaqueous liquid.

In some implementations, the continuous flow process includes mixing thechlorinated aqueous liquid after irradiating with an oxygen radicalgenerating compound.

In some implementations, the oxygen radical generating compound is O₃and/or H₂O₂.

In some implementations, the O₃ and/or H₂O₂ is added at 10-25 times theconcentration of the chlorine and/or the hypochlorous acid salt.

In some implementations, the pretreating further comprises at least oneprocess selected from pre-filtering, acidifying, basifying, andbuffering.

In some implementations, the chlorine and/or sodium hypochlorite areadded at a concentration of 10-50 times the concentration of the MTBE inthe contaminated aqueous liquid.

In some implementations, the light source is a Low Pressure UV lamp or aMedium Pressure UV lamp.

In some implementations, the concentration of MTBE is at least 1 ppm inthe contaminated aqueous liquid and the concentration of MTBE is reducedby more than 92% in the decontaminated aqueous liquid.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is an exemplary graph of a dependence of the ratio of HOCl/OCl⁻on pH (pKa=7.5, at 25° C.).

FIG. 2 is an exemplary diagram of a MTBE Decontamination Reactor.

FIG. 3 is an exemplary graph of a control experiment of a residualpercent MTBE after circulation without treatment.

FIG. 4 is an exemplary graph of an experiment of a residual percent MTBEafter circulation with treatment.

FIG. 5 is an exemplary graph of an experiment of a concentration of TBFafter circulation with treatment.

FIG. 6 is an exemplary graph of an experiment of a residual percent MTBEafter circulation with treatment.

FIG. 7 is an exemplary graph of an experiment of a concentration of TBFafter circulation with treatment.

FIG. 8 is an exemplary graph of an experiment of a residual percent MTBEafter circulation with treatment.

FIG. 9 is an exemplary graph of an experiment of a concentration of TBFafter circulation with treatment.

FIG. 10 is an exemplary graph of an experiment of a residual percentMTBE after circulation with treatment.

FIG. 11 is an exemplary graph of an experiment of a concentration of TBFafter circulation with treatment.

FIG. 12 is an exemplary graph of an experiment of a residual percentMTBE after circulation with treatment.

FIG. 13 is an exemplary graph of an experiment of a concentration of TBFafter circulation with treatment.

FIG. 14 is an exemplary graph of an experiment of a residual percentMTBE after circulation with treatment.

FIG. 15 is an exemplary graph of an experiment of a concentration of TBFafter circulation with treatment.

FIG. 16 is an exemplary graph of an experiment of a residual percentMTBE after circulation with treatment.

FIG. 17 is an exemplary graph of an experiment of degradation byproductsafter circulation with treatment.

FIG. 18 is an exemplary graph of an experiment of a residual percentMTBE after circulation with treatment.

FIG. 19 is an exemplary graph of an experiment of degradation byproductsafter circulation with treatment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views.

The terms “approximately,” “approximate,” “about,” and similar termsgenerally refer to ranges that include the identified value within amargin of 20%, 10%, or 5%, and any values therebetween.

Aspects of the current disclosure are directed to a process fordecontaminating a contaminated aqueous liquid containing one or moreorganic contaminants such as an oxygenated hydrocarbon, e.g.,methyl-tert-butyl ether (MTBE). The contaminated aqueous liquid mayinclude, but is not limited to groundwater, industrial process liquids,and wastewater, or mixtures thereof. The contaminated aqueous liquid ismixed with a chlorine source such as a source of chlorine atoms,including chlorine, a hypochlorite (an ion composed of chlorine andoxygen, with the chemical formula ClO⁻) and/or a hypochlorous acid salt,preferably sodium hypochlorite and/or calcium hypochlorite. Theresultant mixture forms a chlorinated aqueous liquid. The concentrationof chlorine and/or the hypochlorous acid salt, relative to the totalmass of the chlorinated aqueous liquid can be 1-100 ppm, 5-80 ppm, 10-70ppm, 15-60 ppm, 20-50 ppm, or 25-40 ppm. In some implementations, theconcentration of the chlorine and/or the hypochlorous acid salt may begreater than the concentration of the MTBE in the chlorinated aqueousliquid by 2-100 times greater, 5-75 times greater, 10-50 times greater,or 15-25 times greater.

In some implementations, the process includes adjusting the pH of thecontaminated aqueous liquid to a pH of 5-7 before mixing. Adjusting thepH may increase an effectiveness of the process for decontamination ofthe present disclosure by resulting in greater oxidation of organiccontaminants. By adjusting the pH an effectiveness of the process fordecontaminating can improve by at least 25%, by at least 35%, by atleast 45%, by at least 50%. The effectiveness of decontaminating can bemeasured by the increased presence of degradation product in thechlorinated aqueous liquid over time. The pH may be adjusted byacidifying or basifying the contaminated aqueous liquid. The acidifyingmay be accomplished by adding an Arrhenius acid including, but notlimited to an inorganic acid such as hydrochloric acid and/or sulfuricacid, or an organic acid such as acetic acid, propionic acid, or butyricacid. Inorganic acids are preferred to organic acids because organicacids will increase the amount of organic materials present in thechlorinated aqueous liquid, which may reduce the effectiveness of theprocess of decontamination. The basifying may be accomplished by addingan Arrhenius base including, but not limited to sodium hydroxide orpotassium hydroxide. Basifying may also be accomplished by adding aminesincluding, but not limited to methylamine, ethylamine, or pyridine,however FIG. 1 depicts the dependence of the ratio of HOCl/OCl⁻ on pH.The concentration of free chlorine is highly dependent on pH. Freechlorine is the concentration of the chlorine present as hypochloriteion and hypochlorous acid. The higher concentration of HOCl results inmore free chlorine to oxidize an organic contaminant in the aqueoussolution. The present disclosure employs the photooxidation of chlorineand photolysis of hypochlorous acid by utilizing ultraviolet light toinduce an excitation of an electron in an atom of chlorine or moleculeof a hydroxide ion resulting in a chlorine radical and hydroxyl radical.

The chlorinated aqueous liquid is preferably irradiated with UV light.The irradiating may be accomplished with a light source emitting anultraviolent (UV) wavelength of about 254 nm from a monochromatic lightsource. In some implementations the light source may emit approximately220 nm to 300 nm, preferably 235 nm to 280 nm, more preferably 245 nm to265 nm, most preferably 250 nm to 260 nm of light among otherwavelengths, as the case may be with a polychromatic light source. Anexample of a monochromatic light source may be a Xenon, Mercury, or LEDlight source filtered by a diffraction grating or prism monochrometer toform a single wavelength or a narrow range of at most 15 nm, at most 10nm, at most 5 nm, or at most 2 nm centralized around 254 nm. Anotherexample may be a low pressure mercury lamp. In some implementations thepolychromatic light source may be Xenon, Mercury, or LED. An example ofa polychromatic light source may be a medium pressure mercury lamphaving wavelengths between 200 nm and 370 nm. The light source may alsobe categorized by UV-A wavelengths (320 nm to 290 nm), UV-B wavelengths(290 nm to 320 nm), or UV-C wavelengths (100 nm to 400 nm). The lightsource power, intensity and exposure time of UV light determines theefficiency of the decontaminating of the contaminated aqueous liquid. Insome implementations, the light source power is between 5-300 W, between15-275 W, between 25-250 W, between 75-200 W, and between 100-175 W. Insome implementations, the light source has intensity between 1×10⁻³W/cm²-15×10⁻² W/cm², between 5×10⁻³ W/cm²-10×10⁻² W/cm², and between6×10⁻³ W/cm²-8×10⁻² W/cm². In some implementations, the irradiatingtakes place for an exposure time of at least 1-60 minutes, at least 5-50minute, at least 10-40 minutes, and at least 15-30 minutes. In someimplementations, the light source power, emitted wavelength range,intensity, and exposure time can be adjustable. In some implementationsthe light source may be pulsed at a plurality of frequencies including,but not limited to at least 50 s⁻¹, at least 100 s⁻¹, at least 150 s⁻¹,at least 200 s⁻¹, at least 250 s⁻¹, at least 300 s⁻¹, at least 350 s⁻¹,at least 500 s⁻¹, at least 750 s⁻¹, at least 1000 s⁻¹, at least 1500s⁻¹. In some implementations, the light source may be pulsed with aplurality of wavelengths of UV light. In some implementations a lightfrom the light source may be polarized.

Irradiating the chlorinated aqueous liquid with UV light can produce aradical molecular species that reacts with the MTBE to oxidize the MTBEand form at least one degradation byproduct selected from the groupconsisting of tert-butyl formate (TBF), tert-butyl alcohol (TBA),acetone, carbon dioxide and water and forms a decontaminated aqueousliquid. As used herein, “decontaminated” is defined as removal of MTBEto a concentration preferably less than 100 ppb. Although degradationproducts of MTBE may remain in the decontaminated aqueous liquid,biologically activated filtration techniques that use microorganisms,fungi, yeast and other biological elements familiar to those skilled inthe art can be used to remove the degradation products or furtheroxidize the degradation products to carbon dioxide and water.

The radical species may include, but is not limited to at least one of ahydroxyl radical and chlorine radical. The decontaminated aqueous liquidhas a lower concentration of MTBE than the concentration of MTBE in thecontaminated aqueous liquid. In some implementations, the concentrationof MTBE in the contaminated aqueous liquid is at least 1 ppm, is atleast 10 ppm, is at least 15 ppm, is at least 25 ppm, is at least 50ppm, is at least 100 ppm, is at least 500 ppm, is at least 1000 ppm. Theconcentration of MTBE is reduced in the decontaminated aqueous liquid bymore than 10%, more than 20%, more than 30%, more than 40%, more than50%, more than 60%, more than 70%, more than 80%, more than 90%, andmore than 95%.

In some implementations, the irradiating and the mixing with thechlorine source may occur simultaneously.

In some implementations, at least one NORMAG™ photoreactor may be usedto irradiate the chlorinated aqueous liquid. In some implementations theBersen InLine® may be used to irradiate the chlorinated aqueous liquid.

An apparatus containing the light source that emits the ultraviolent(UV) light may take several forms in addition to the NORMAG photoreactorand the Bersen InLine®. In some implementations, the apparatus mayencase at least one light source in a UV permissive casing in anelongated cubic shape or cylindrical shape. The apparatus may also takethe form of at least one fiber optic. In some implementations, multiplefiber optic fibers may be bundled to form a multiple point tree-likestructure that is gathered at a central point forming a trunk andbranches of each fiber optic fiber with a light emitting end of thefiber optic directed away from the trunk like a ray. Each fiber opticend may extend out and around the circumference of the trunk of bundledfiber optic fibers. The light in the cylindrical shape, elongated cubicshape, or fiber optic may be submerged into a container holding thechlorinated aqueous liquid. The container may have an inflow port and anoutflow port through which the chlorinated aqueous liquid may enter tobe irradiated by the light source in the apparatus and then exit afterirradiation. The apparatus may also be suspended above and directedtoward the container holding the chlorinated aqueous liquid at adistance above a surface of the chlorinated aqueous liquid of less than50 cm, less than 30 cm, less than 20 cm, less than 10 cm, less than 5cm. In some implementations the container is transparent to UV light andthe apparatus containing the light source may surround at least onecontainer holding the chlorinated aqueous liquid and direct the lightinto at least one container.

In some implementations, the process further includes mixing thechlorinated aqueous liquid after irradiating with an oxygen radicalgenerating compound. In some implementations, the oxygen radicalgenerating compound is O₃ and/or H₂O₂. O₃ and H₂O₂ are known to produceoxygen radicals and may scavenge and remove chlorine and further oxidizethe degradation products. In some implementations, the O₃ and/or H₂O₂ isadded at a concentration that exceeds the concentration of the chlorineand/or the hypochlorous acid salt in the chlorinated aqueous liquid byat least 5 times the concentration, at least 10 times the concentration,at least 15 times the concentration, at least 20 times theconcentration, at least 25 times the concentration, at least 30 timesthe concentration, at least 35 times the concentration. In someimplementations the process further includes filtering through anactivated carbon or biologically active filters to remove remnantdegradation products of MTBE that may have remained unoxidized bychlorine radicals, oxygen radicals, or hydroxyl radicals.

According to another aspect, the present disclosure relates to acontinuous flow process for decontaminating the contaminated aqueousliquid, e.g., an aqueous liquid comprising methyl-tert-butyl ether(MTBE). The continuous flow process includes flowing the contaminatedaqueous liquid comprising water and MTBE while pretreating thecontaminated aqueous liquid with chlorine and/or a hypochlorous acidsalt to form a chlorinated aqueous liquid. Next, the chlorinated aqueousliquid is irradiated with a light source having a wavelength of about254 nm. The light source may be from either a monochromatic light sourcethat generates approximately 254 nm wavelength of light or from apolychromatic light source having wavelengths between approximately 200nm and 370 nm, to produce a radical molecular species that degrades theMTBE thus resulting in a decontaminated aqueous liquid. The MTBE can bedegraded into at least one degradation byproduct, for example, selectedfrom the group consisting of tert-butyl formate (TBF), tert-butylalcohol (TBA), acetone, carbon dioxide and water.

The continuous flow process of the present disclosure refers to acontinuous flow process that involves a pretreatment stage and anirradiation stage. As depicted in FIG. 2, the pretreatment stage andirradiation stage may each take place in separate vessels, such that thepretreatment stage takes place in a pretreatment vessel 204 and theirradiation stage takes place in an irradiation vessel 206. Upstream ofthe pretreatment vessel 204 can be a contaminated aqueous liquid holdingvessel 202 which holds the contaminated aqueous liquid before thecontaminated aqueous liquid flows into the pretreatment vessel 204.Downstream of the irradiation vessel may be a decontaminated aqueousliquid holding vessel 208, which holds the decontaminated aqueous liquidafter irradiation. Each vessel may be part of an MTBE decontaminationreactor 200 in which the continuous flow process of the presentdisclosure may take place.

In some implementations, the pretreating may include any one or more ofpre-filtering, acidifying, basifying, and buffering. In someimplementations, at least one of the pre-filtering, acidifying,basifying, and buffering may occur before pretreating the contaminatedaqueous liquid with chlorine and/or a hypochlorous acid salt.

Pre-filtering may employ several filters including, but not limited toindustrial sub-micron filters, a coarse screen filter, a carbon filter,and an oil filter. Because the contaminated aqueous liquid may be from avariety of sources, the pre-filtering may be necessary to removeparticulate matter and long-chain fatty organic molecules that cannot bedecontaminated through the continuous flow process of the presentdisclosure. The pre-filtering may occur in a single stage or multiplestages of the continuous flow process. For example, the pre-filteringmay first continuously flow the contaminated aqueous liquid through apiping system and through a plurality of stages of the coarse filter toremove particles of greater than 0.5 mm, 50 microns, and 1 micron, thenfiltering through a sub-micron filter, then filtering through an oilfilter, and finally an activated carbon filter. The pre-filtering mayoccur while the contaminated aqueous liquid is flowing into thepretreatment vessel 203, but may occur at any point upstream of thepretreatment vessel.

Acidifying may include adding the Arrhenius acid to change the pH of thecontaminated aqueous liquid to approximately pH 1-10, to approximatelypH 3-8, or preferably to approximately pH 5-7. The Arrhenius acid mayinclude, but is not limited to hydrochloric acid and sulfuric acid.

Basifying may include adding the Arrhenius base to change the pH of thecontaminated aqueous liquid to approximately pH 1-10, to approximatelypH 3-8, or preferably to approximately pH 5-7. The Arrhenius base mayinclude, but not limited to sodium hydroxide and potassium hydroxide.Basifying may include adding amines which may include, but are notlimited to methylamine, ethylamine, and pyridine.

Buffering may include adding a buffering agent to the contaminatedaqueous liquid to maintain the pH approximately between pH 5 and pH 7. ApKa of the buffering agent is preferably between the range of pH to bemaintained in order to be effective. Using the Hendersen-Hasselbachequation the buffering agent proportions can be determined. Thebuffering agent may be added in conjunction with acidifying or basifyingbut may be added independently as well. The buffering agent may include,but is not limited to cacodylate, maleate, sodium phosphate, and sodiumhydrogen phosphate.

In some implementations, the acidifying, basifying and buffering canoccur while the contaminated aqueous liquid is in the pretreatmentvessel, whereas, the pre-filtering may necessitate that the contaminatedaqueous liquid to be flowing into the pretreatment vessel to completethe pre-filtering.

In some implementations of the continuous flow process fordecontamination may use the concentration of chlorine and/or thehypochlorous acid salt as described above. In some implementations, theconcentration of the chlorine and/or the hypochlorous acid salt may begreater than the concentration of the MTBE in the chlorinated aqueousliquid as described above.

In the irradiation stage of the continuous flow process, in someimplementations, the light source is a Low Pressure UV lamp or a MediumPressure UV lamp. The light source may be oriented in various ways toirradiate the chlorinated aqueous liquid. In some implementations, thelight source may be encased in a UV permissive material protected fromany liquid penetration, shaped in an elongated cylinder or cube, asdescribed above. In some implementations of the continuous process, theelongated cylinder or cube may be inserted perpendicularly through thecross section of the piping system through which the chlorinated aqueousliquid flows and may be irradiated. In some implementations, at leastone light source may be inserted through a center of the piping system,parallel to the longitudinal axis of the piping system. In someimplementations the light source may be suspended above a transparentand UV-permissive piping system, through which the chlorinated aqueousliquid flows and can be irradiated. In some implementations the lightsource may be directed into the piping system by a light guide or froman assembly that is perpendicular to the piping system. In someimplementations the piping system can recirculate the chlorinatedaqueous liquid and the chlorinated aqueous liquid can continuously beirradiated by the light source in any of the above describedimplementations.

In some implementations, the chlorinated aqueous liquid may flow fromthe pretreatment vessel into the irradiation vessel. Within theirradiation vessel, at least one light source may be submerged into thevessel when filled with the chlorinated aqueous liquid to irradiate thechlorinated aqueous liquid. In some implementations the irradiationvessel may also be equipped with a mixer and pump to circulate thechlorinated aqueous liquid while it is irradiated by the light source.

In some implementations, at least one NORMAG™ photoreactor may be usedto irradiate the chlorinated aqueous liquid. In some implementations theBersen InLine® unit may be used to irradiate the chlorinated aqueousliquid. For example, as the chlorinated aqueous liquid flows out of thepretreatment vessel, the chlorinated aqueous liquid may flow through theBersen InLine®. Several Bersen InLine® units may be placed in paralleland act as the irradiation vessel 206 such that the irradiating isoccurring during flow from the pretreatment vessel 204 to thedecontaminated aqueous liquid holding vessel 208.

In some implementations, the concentration of MTBE in the contaminatedaqueous liquid is at least 1 ppm, is at least 10 ppm, is at least 15ppm, is at least 25 ppm, is at least 50 ppm, is at least 100 ppm, is atleast 500 ppm, is at least 1000 ppm. The concentration of MTBE isreduced in the decontaminated aqueous liquid by more than 10%, more than20%, more than 30%, more than 40%, more than 50%, more than 60%, morethan 70%, more than 805, more than 90%, and more than 95%.

In some implementations, the continuous flow process includes mixing thechlorinated aqueous liquid after irradiation with an oxygen radicalgenerating compound. In some implementations, the oxygen radicalgenerating compound is O₃ and/or H₂O₂. In some implementations, the O₃and/or H₂O₂ is added at a concentration that exceeds the concentrationof the chlorine and/or the hypochlorous acid salt in the chlorinatedaqueous liquid by at least 5 times the concentration, at least 10 timesthe concentration, at least 15 times the concentration, at least 20times the concentration, at least 25 times the concentration, at least30 times the concentration, at least 35 times the concentration. In someimplementations, the chlorinated aqueous liquid may receive a secondexposure to the light source after the oxygen radical generating ismixed into the chlorinated aqueous liquid.

In some implementations, the continuous flow process further includesfiltering through an activated carbon or biologically active filters toremove remnant degradation products of MTBE that may have remainedunoxidized by chlorine radicals, oxygen radicals, or hydroxyl radicals.In some implementations filtering through activated carbon orbiologically active filters may occur downstream of the irradiationvessel 206, but upstream of the decontaminated aqueous liquid holdingvessel 208, 207 in FIG. 2.

In some implementations, the continuous flow process may employ acontroller system to do at least one of adding chlorine and/or ahypochlorous acid salt, adding the oxygen radical generating compound,acidifying, basifying, and buffering. In some implementations, thecontroller system may determine a quantity to add by interpreting asignal produced by an instrument that is connected to the controllersystem. The instrument may include, but is not limited to at least onechemical analysis instrument such as a gas chromatographer, an highpressure liquid chromatographer, a mass spectrometer, a pH meter, and aspectrophotometer.

The examples below are intended to further illustrate thedecontamination of the contaminated aqueous liquid comprisingmethyl-tert-butyl ether and are not intended to limit the scope of theclaims.

Example 1 Method and Materials Chemicals and Solutions

Sigma Aldrich HPLC grade, 99.999% purity of MTBE, Tert-Butyl Formate(TBF), and 5.25% sodium hypochlorite were purchased from local chemicalvendors in Saudi Arabia.

Deionized water from Mili-Q direct purification system was used forpreparation of 100 ppm MTBE, and 1000 ppm free chlorine stock solutions,from which water was spiked prior to treatment. The flask was stopperedtightly and wrapped with the aluminum foil and then kept in therefrigerator at 4° C. The desired concentration of MTBE was diluted intothe experimental vessel from the prepared stock solution. Sodiumhydroxide (NaOH) pellets, 98% concentrated sulfuric acid were obtainedfrom Merck, and DPD (N, N diethyl-p-phenylenediamine) Tablet NO.1 werealso utilized.

Photo-Reactor Setup

Batch experiments were carried out in a NORMAG® tubular photoreactorwith forced liquid circulation. The photoreactor vessel has a totalvolume of 470 ml and housed with two types of ultraviolet mercury lamps:namely Low pressure and medium pressure lamps obtained from Heraeus(Heraeus Noblelight America, LLC, Gaithersburg, Md.). As per themanufacturer, low pressure lamps (LP) emit radiation at a wavelength of254 nm with intensity of 6.5×10⁻³ W/cm² from 15 Watt power source (TNN15/32, 55 Volts, Cat No. SAA 09370); and medium pressure lamps (MP)deliver a broadband spectrum over the complete range of 200-400 nm withintensity of =5.3×10⁻² W/cm² from 150 Watt power source (TQ 150, 85Volts, Cat No. SAA 09360). LP lamp produces a spectrum mainly at 254 nmand it can be described practically as monochromatic. It was shown thatthe MP lamp gives much weaker intensity at 254 nm wavelength, but it hassignificant UV-peaks at higher wavelengths including 365 nm. The MP lampalso emits very strong peaks within the Visible-region.

Experiment Design

Several bench scale experiments were conducted based on the followingexperimental design: (a) blank run: circulation of MTBE spiked deionizedwater alone to account for the loss of MTBE due to volatilization, (b)treatment of MTBE spiked water by a combination of free chlorine aloneat 10, 25, 50 ppm and pH of 5, 7, and 9, (c) treatment of MTBE spikedwater by a combination of UV lamp type, chlorine dosages (2-50 ppm), andpH 5, 7, and 9. Finally, the optimized conditions were tested on thenatural groundwater spiked with MTBE. The natural groundwater sample wasobtained from a well located in Dhahran, Saudi Arabia. During eachexperiment run, the water spiked with 1000 ppb MTBE was circulated for10 minutes to ensure uniform dilution of MTBE in the reactor beforestarting the treatment and collecting the first sample at time zero(before treatment). Then, the desired amount of chlorine was injectedand in the meantime the selected lamp type was turned on. In allexperiment, water samples were collected at treatment time of 5, 10, 15,30 minutes and tested for the MTBE residual, degradation byproducts, andchlorine residual. About 5 ml of 0.01N sodium thiosulfate is required todechlorinate 5 ppm of residual chlorine in the effluent beforedischarge.

Analytical Methods

Water samples were collected from the UV photoreactor before and afterthe treatment and analyzed for its concentration levels of MTBE anddegradation byproducts by using an ISQ single quadrupole GC/MS system(Thermo Scientific) equipped with TriPlus for headspace injectionsystem. A 60 m long, 0.32 mm i.d. Rtx-502.2 (Restek Corp., USA)capillary column was used for the separation purpose. The carrier gaswas helium flowing at the rate of 1.7 mL·min⁻¹. The column temperaturewas programmed to rise from 50 to 220° C. at the rate of 20° C.·min⁻¹.The mass spectrometer was operated in the selected ion mode (SIM).Calibration curves were prepared for MTBE and some by-products (BSTawabini, 2014). 1 mL of the collected water samples was immediatelytransferred to the head space Thermo Scientific standard vials andplaced in the Autosampler sequences for the analysis of MTBE, anddegradation byproducts. The GC/MS output was acquired, stored, andprocessed by Thermo Scientific™ Xcalibur software programmed. Residualchlorine level was monitored using Analytik Jena's UV/Visspectrophotometer SPECORD® 50 using DPD method. Duplicate analysis wascarried out for each sample.

Example 2 Results and Discussion

Blank runs were conducted to estimate the loss of MTBE due to stirringalone. In this experiment, 1000 ppb of MTBE was spiked into deionizedwater, and continuously circulated for 30 minutes at a constant flowrate (i.e. 30% of the pump capacity) in the closed system ofphotoreactor. The blank runs were conducted under different pHconditions to observe the pH effects. A loss of about 2% of MTBE at pH 5and a loss of 1%-2% of MTBE at pH 7 and 9 was observed while circulatingin the closed system for 30 minutes (FIG. 2). In the present disclosure,the loss of MTBE was very minimal. This could be due to the low MTBEconcentration (i.e., 1 ppm) used in the present disclosure. Constantroom temperature was maintained in this study. There was no degradationof MTBE due to the circulation alone, which is confirmed by thenonappearance of the degradation byproducts.

Example 3 Removal of MTBE by Chlorine Alone Effect of pH on MTBE RemovalEfficiency by Chlorine Alone

The pH effect on the degradation of MTBE with 25 ppm of free chlorinealone was investigated. The pH effect on the degradation of MTBE wasobserved that about 63.6%, 42%, and 58% of MTBE were chemically oxidizedby 25 ppm of free chlorine alone at pH 5, 7, and 9 after 30 minutes,respectively. By comparison the removal of MTBE was the most at pH 5(FIG. 4). This is due to the presences of 99.7% hypochlorous acid atacidic pH which is also more effective than hypochlorite fordisinfection of harmful microorganisms in drinking water treatmentplant. The reactivity of chlorine with organic depends on the pH of theaqueous solution. Hypochlorous acid is a dominant reactive species withmost organic compounds due to its oxidizing power and chemical structurecharacterized by Cl—O bond polarization. The monitored degradationbyproduct (i.e., TBF) confirmed that at pH 5, hypochlorous can oxidizeMTBE to some extent. The MTBE degradation mechanism by chlorine alonemight be due to either of the following mechanism or combination ofthem: (i) oxidation reactions, (ii) addition reactions to unsaturatedbonds, (iii) electrophilic substitution reactions at nucleophilic sites.The highest TBF measurement was observed at pH 5, reaching to about 500ppb between 5 and 15 minutes of contact time (FIG. 5). However, after 15minutes a slight decline of TBF was observed that might be due to thechemical oxidation, which might also have happened between TBF and freechlorine species. The same trend was seen at pH 7 and 9 but havingdifferent level of TBF (pH 5 greater than pH 7 greater than pH 9) (FIG.5). Comparing the reaction time required to degrade certain level ofMTBE to TBF, and other byproducts, shorter time was observed at pH 5than at pH 7 and 9. In all the cases, a substantial level of TBFproduction was recognized within 5 minutes reaction time.

Effect of Chlorine Dosage on MTBE Removal Efficiency by Chlorine Alone

Chlorine is one of the potential chemical oxidants with 1.49 oxidationpower. Liquid chlorine in the form of sodium hypochlorite is a widelyused form of chlorine in water and wastewater treatment. The MTBEdegradation efficiency of 52%, 64%, and 64% of MTBE removal was observeddue to 10, 25, and 50 ppm of free chlorine alone after 30 minutes oftreatment time, respectively (FIG. 6). The dose effect between 25 and 50ppm of free chlorine did not show significant difference. This might bedue to the low MTBE concentration available to react with excess freechlorine (i.e., 50 ppm). However, increasing the free chlorine dose from10 ppm to 25 ppm has increased the MTBE removal efficiency from 52% to64% after 30 minutes of treatment time. 25 ppm of free chlorine wasselected as a dose to react 1000 ppb of MTBE in this study. Themechanism of MTBE degradation by free chlorine alone was discussedabove.

Like other chemical oxidants such as OH, O₃, MNO₄, and S₂O₄, chlorinespecies able to degrade MTBE to byproducts (TBF, TBA, and acetone).Theoretically carbon dioxide and water are the final degradation ofMTBE; however MTBE degradation involves multi-chain reactions. Thetransformation of MTBE to TBF was a dominant event and concurrently TBFalso oxidized to TBA and acetone. TBF was the dominant byproductobserved. The level of TBF reached to 500-600 ppb between 5-10 minutesof treatment time when 25 and 50 ppm free chlorine alone was applied(FIG. 7).

Example 4 Removal of MTBE by UV/Chlorine Process

To understand the set of conditions under which MTBE is removed from theaqueous solution, treatment parameters such as oxidant dosages, pH, UVtype, and contact time were varied and their impacts on the removalefficiency of MTBE by UV/chlorine was determined.

Effect of pH on MTBE Removal Efficiency by LP UV/Chlorine

The availability of free chlorine species in the water depends on thesolution's pH. At the acidic pH condition hypochlorous acid (OCl⁻) isabundant while in alkali solution hypochlorite (OCl⁻) is dominant. Inthis study, pH 5, 7, and 9 were used to assess the effectiveness of freechlorine based advanced oxidation process to degrade MTBE in water.Another experimental conditions used were: LP UV, chlorine dosage (5,10, 25 ppm), 30 minutes exposure time, and 1000 ppb initialconcentrations of MTBE. At pH 5, the MTBE removal is slightly betterthan pH 7 and 9 (FIG. 8). In general, regardless of pH effect, MTBE canbe completely degraded to TBF and other byproducts by LP UV and 25 ppmof free chlorine after 30 minutes. The removal mechanism of theUV/chlorine could be due to the synergistic effect of thiosulfate, UVphotolysis, radical oxidation, and chemical oxidation by free chlorine.The dominant reacting radical mainly generated from the UV/chlorine AOPis hydroxyl (OH.) in addition to chlorine radical. The reaction of HOClwith OH radical was determined as 8.5×10⁴ M⁻¹·s⁻¹ which indicates thelesser scavenging effect than H₂O₂ with OH radical having reaction rateof 2.7×10⁷ M⁻¹·s⁻¹ during the photolysis of free chlorine at a pHgreater than pH 5.5. The higher .OH radical formation in irradiated HOClsolutions, relative to hydrogen peroxide, may be a function of highermolar absorption coefficients of HOCl between 220 nm and 320 nm. FIG. 9presented the degradation byproduct (i.e., TBF) generated at pH 5, 7,and 9. It was observed that some of the TBF was also degraded to otherbyproducts like TBA, and acetone after 15 minutes.

Effect of pH on MTBE Removal Efficiency by MP UV/Chlorine

MP UV lamp and 25 ppm of free chlorine were used to degrade MTBE fromsynthetic water having a pH of 5, 7, and 9 and 30 minutes treatment time(FIG. 10). Greater performance of MTBE degradation was observed at pH 5than pH 7, and pH 9. This might be due to the 99.7% of HOCl available atpH greater than 5.5 and the lower scavenging rate of OH radicals. Thedegradation mechanism could be dominantly due to OH radical. The effectof pH 7 and pH 9 were overlapping. This confirmed that MP UV withchlorine can degrade MTBE also at neutral and basic condition. MTBEdegradation with MP UV/chlorine shows 35-42% improvement comparing withMP UV alone and 25 ppm free chlorine alone at pH 5 (FIG. 10). The MTBEdegradation pattern was seen as MP UV/free chlorine greater than freechlorine alone greater than MP UV alone after 5 minutes treatment time.The MP UV/free chlorine at pH 5 has also resulted in the minimal TBFconcentration (FIG. 11). The minimal TBF concentration could be due tothe indiscriminate reaction of OH radicals with all the organics presentin the synthetic water. Regardless of pH effect the TBF level generateddeclined after 10 minutes of treatment time. It might be possible tocompletely degrade TBF by increasing the treatment time.

Effect of Chlorine Dosage on MTBE Removal Efficiency by LP UV/Chlorine

The higher chlorine dosage shows better degradation at 5-10 minutes oftreatment time. However, after 15 minutes the lower dose (10 ppm) andthe moderate dose (25 ppm) were able to degrade MTBE completely (FIG.12). The lower degradation efficiency observed at 50 ppm of freechlorine might be due to a scavenging effect of excess HOCl. Thescavenging effect of excess HOCl favors the lower dose of free chlorineduring UV/chlorine AOP because the scavenging effect minimizes therequired thiosulfate for quenching the residual chlorine. In the presentdisclosure, greater than 95% of MTBE removal was obtained at benchscale. The monitored degradation byproduct (i.e., TBF) was seenincreasing until 10 minutes and then declined to some extent (FIG. 13).

Effect of Chlorine Dosage on the Degradation of MTBE with MP UV (150Watt) Irradiation/Chlorine

The differences in MTBE degradation between the three chlorine doses(i.e., 2, 5, 10 ppm) used were insignificant, however, after 5 minutesof exposure time, 10 ppm of chlorine showed a better MTBE removalefficiency than other doses (FIG. 14). This could be due to the yield ofthe radicals generated during the process. MP UV/chlorine was able todegrade MTBE completely and the generated byproducts after 30 minutes.The efficiency of MTBE degradation with MP UV alone may have beenimproved due to the OH. radicals mainly generated from the free chlorinewhich may indiscriminately react with MTBE and may have producedbyproducts in the synthetic groundwater sample (FIG. 15).

Example 5 Removal of MTBE in Natural Groundwater Sample

The conditions which produced the lowest MTBE in the syntheticgroundwater sample experiment was tested on natural groundwatercollected from inside King Fahd University of Petroleum and Minerals(KFUPM) main campus, Dhahran, Saudi Arabia. The conditions whichproduced the lowest MTBE concentrations were LP UV, 10 ppm, and pH 5. Atthese conditions greater than 99% MTBE removal efficiency was obtained,and it was efficient in comparison to the MP UV/chlorine process asdepicted in FIG. 16 and FIG. 18. The data depicted in FIG. 16 and FIG.18 implicate that MTBE removal efficiency was improved by at least 90%than MTBE removal by UV/H₂O₂ which may be due to higher OH-radical yieldand less scavenging effect. LP UV shows superior MTBE removal efficiencyover the MP UV in terms of the low level of byproducts generated, andreduced energy requirement (FIG. 17). The low level of byproductsgenerated and reduced energy requirement might be due to the differenceof oxidant used, and low radical (OH) scavenging effect of hypochlorousacid.

MTBE removal efficiency by UV/chlorine advanced oxidation was carriedout under various treatment conditions. Accordingly, the conditionsunder which the results were obtained were LP UV/chlorine at 10 ppmchlorine, pH 5, 30 minutes, and Electrical Energy Order (EEO) of 4.01kWh/m³. The conditions were also tested on natural groundwater samplesand greater than 99% MTBE removal efficiency was detected. LP UV AOP maybe an improvement MP UV because of the low electrical energy ordermeasured though MP UV/chlorine AOP, which can also degrade MTBE fromsynthetic groundwater samples and natural groundwater samples. Thegreater than 99% MTBE removal efficiency can be explained by the LP UVemission spectrum. The LP UV emission spectrum is a monochromaticradiation spectrum at 254 nm, and MTBE ability to absorb the emittedradiation at this wavelength may have contributed to the MTBEdegradation. MTBE degradation by UV/chlorine followed the first orderreaction rate. TBF degradation byproducts were as abundant as MTBEdegradation byproducts (FIG. 19).

1: A process for decontaminating a contaminated aqueous liquid comprising methyl-tert-butyl ether (MTBE), comprising: mixing chlorine and/or a hypochlorous acid salt with the contaminated aqueous liquid to form a chlorinated aqueous liquid comprising 10-50 ppm of chlorine and/or the hypochlorous acid salt, relative to the total mass of the chlorinated aqueous liquid; and irradiating the chlorinated aqueous liquid with light having a wavelength of about 254 nm from a monochromatic light source that generates a 254 nm wavelength of light or with a polychromatic light source having wavelengths between 200 nm and 370 nm to oxidize the MTBE and form at least one degradation byproduct selected from the group consisting of tert-butyl formate (TBF), tert-butyl alcohol (TBA), acetone, carbon dioxide and water, and form a decontaminated aqueous liquid. 2: The process of claim 1, further comprising mixing the chlorinated aqueous liquid with an oxygen radical generating compound. 3: The process of claim 2, wherein the oxygen radical generating compound is O₃ and/or H₂O₂. 4: The process of claim 3, wherein the O₃ and/or H₂O₂ is present at 10-25 times the concentration of the chlorine and/or the hypochlorous acid salt in the chlorinated aqueous liquid. 5: The process of claim 1, wherein the concentration of the chlorine and/or sodium hypochlorite is 10-50 times the concentration of the MTBE in the chlorinated aqueous liquid. 6: The process of claim 1, further comprising adjusting the pH of the contaminated aqueous liquid to a pH of 5-7 before the mixing. 7: The process of claim 6, further comprising adjusting the pH with hydrochloric acid, sulfuric acid, or sodium hydroxide. 8: The process of claim 1, wherein the light source power is between 10-200 W. 9: The process of claim 1, wherein the light source has an intensity between 5×10⁻³ W/cm²-7×10⁻² W/cm². 10: The process of claim 1, wherein the radical molecular species is at least one of a chlorine radical and a hydroxyl radical. 11: The process of claim 1, wherein the concentration of MTBE is at least 1 ppm in the contaminated aqueous liquid and the concentration of MTBE is reduced by more than 92% in the decontaminated aqueous liquid. 12: The process of claim 1, wherein chlorine is removed from the decontaminated aqueous liquid by thiosulfate, UV photolysis, radical oxidation, and chemical oxidation by free chlorine. 13: A continuous flow process for decontaminating a contaminated aqueous liquid comprising methyl-tert-butyl ether (MTBE), comprising: flowing the contaminated aqueous liquid while pretreating the contaminated aqueous liquid with chlorine and/or a hypochlorous acid salt to form a chlorinated aqueous liquid comprising 10-50 ppm of chlorine and/or the hypochlorous acid salt, relative to the total mass of the chlorinated aqueous liquid; and irradiating the chlorinated aqueous liquid with light having a wavelength of about 254 nm from a monochromatic light source that generates a 254 nm wavelength of light or with a polychromatic light source having wavelengths between 200 nm and 370 nm to produce a radical molecular species that degrades the MTBE into at least one degradation byproduct selected from the group consisting of tert-butyl formate (TBF), tert-butyl alcohol (TBA), acetone, carbon dioxide and water and forms a decontaminated aqueous liquid; wherein a concentration of MTBE in the contaminated aqueous liquid is higher than a concentration of MTBE in the decontaminated aqueous liquid. 14: The continuous flow process of claim 13, further comprising mixing the chlorinated aqueous liquid after irradiating with an oxygen radical generating compound. 15: The continuous flow process of claim 14, wherein the oxygen radical generating compound is O₃ and/or H₂O₂. 16: The continuous flow process of claim 15, wherein the O₃ and/or H₂O₂ is added at 10-25 times the concentration of the chlorine and/or the hypochlorous acid salt. 17: The continuous flow process of claim 13, wherein the pretreating further comprises at least one process selected from pre-filtering, acidifying, basifying, and buffering. 18: The continuous flow process of claim 13, wherein the chlorine and/or sodium hypochlorite are added at a concentration of 10-50 times the concentration of the MTBE in the contaminated aqueous liquid. 19: The continuous flow process of claim 13, wherein the light source is a Low Pressure UV lamp or a Medium Pressure UV lamp. 20: The continuous flow process of claim 13, wherein the concentration of MTBE is at least 1 ppm in the contaminated aqueous liquid and the concentration of MTBE is reduced by more than 92% in the decontaminated aqueous liquid. 